A US expert says innovation is the best way to tackle a changing climate.

Last night, Professor Molly Jahn from the University of Wisconsin delivered the RD Watt lecture at the University of Sydney saying innovation in agricultural and food systems is imperative for society's survival and development.

Professor Jahn has worked extensively in developing countries to link crop breeding with improved human nutrition and welfare.

She says that lately the US projects she is involved in illustrate the big challenges to farmers due to a rapidly changing climate.

"We have to understand the demands that we are making on our agricultural system in not just present but future conditions," she said.

"One thing we know all over the world is that those conditions are changing and they are changing fast.

"In Wisconsin, where I live, the growing season has shifted nearly a month in the past 50 years.

"We have many more extreme rainfall events and I work closely with our farmers to make sure that they have what they need to be successful as farmers in a changing climate.

"In our community, regardless of political orientation, it is not about belief, it is just practical considerations.

"They know conditions are changing and our farmers are taking the lead to make sure the researchers deliver what they need."

But Professor Jahn says that creates opportunities for agricultural research to contribute to moving food systems toward long-term sufficiency and resilience.